Semiconductor device

ABSTRACT

A semiconductor device may include, but is not limited to, a first signal line, a second signal line, and a first shield line. The first signal line is supplied with a first signal. The first signal is smaller in amplitude than a potential difference between a power potential and a reference potential. The second signal line is disposed in a first side of the first signal line. The second signal line is supplied with a second signal. The second signal is smaller in amplitude than the potential difference. The first shield line is disposed in a second side of the first signal line. The second side is opposite to the first side. The first shield line reduces a coupling noise that is applied to the first shield line from the second side.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a semiconductor device. Morespecifically, the present invention relates to a dynamic random accessmemory, hereinafter referred to a DRAM.

Priority is claimed on Japanese Patent Application No. 2008-278797,filed Oct. 29, 2008, the content of which is incorporated herein byreference.

2. Description of the Related Art

In semiconductor devices such as DRAMs, local input/output (I/O) linesextend in parallel to each other. The local input/output (I/O) lines areadjacent to each other with a small distance between those. In somecases, four local input/output (I/O) lines are placed side by side. Acoupling noise is caused by two adjacent local input/output (I/O) lines.In some cases, a first local input/output (I/O) line may be adjacent tosecond and third local input/output (I/O) lines. Namely, the first localinput/output (I/O) line may be disposed between the second and thirdlocal input/output (I/O) lines. In this case, the first localinput/output (I/O) line may in general cause coupling noises with thesecond and third local input/output (I/O) lines. It has been desired tosuppress or reduce the coupling noises between two adjacent localinput/output (I/O) lines. A typical method of suppressing such acoupling noise has been proposed. There is disposed a shield wiring linewhich is adjacent to a signal line that receives a coupling noise.

Japanese Unexamined Patent Application, First Publication, No.JP-A-2003-7860 discloses a technique of disposing signal lines, whichhave an electric potential that is fixed to the power supply potentialor ground potential, on both sides.

Japanese Unexamined Patent Application, First Publication, No.JP-A-2005-332903 discloses a technique of disposing wiring lines, whichhave a predetermined fixed electric potential during a period for whicha coupling noise is received, on both sides.

SUMMARY

In one embodiment, a semiconductor device may include, but is notlimited to, a first signal line, a second signal line, and a firstshield line. The first signal line is supplied with a first signal. Thefirst signal is smaller in amplitude than a potential difference betweena power potential and a reference potential. The second signal line isdisposed in a first side of the first signal line. The second signalline is supplied with a second signal. The second signal is smaller inamplitude than the potential difference. The first shield line isdisposed in a second side of the first signal line. The second side isopposite to the first side. The first shield line reduces a couplingnoise that is applied to the first shield line from the second side.

In another embodiment, a semiconductor device may include, but is notlimited to, a plurality of signal lines and at least one line. Theplurality of signal lines extends substantially in parallel to eachother. The plurality of signal lines is given signals that are smallerin amplitude than a potential difference between a power potential and aground potential. The at least one line is maintained at a fixedpotential. The at least one line is disposed in an opposite side of oneof the signal lines to a side in which another of the signal lines isdisposed.

In still another embodiment, a semiconductor device may include, but isnot limited to, a plurality of signal lines and at least one shieldline. The plurality of signal lines extends substantially in parallel toeach other. The plurality of signal lines is given signals that aresmaller in amplitude than a potential difference between a powerpotential and a reference potential. The at least one shield line ismaintained at a fixed potential. Each of the plurality of signal linesis disposed between adjacent another of the plurality of signal linesand any one of the at least one shield line and a signal-line-free area.The signal-line-free area is free of the others of the plurality ofsignal lines and also free of any signal line which is given a signalthat is smaller in amplitude than the potential difference.

BRIEF DESCRIPTION OF THE DRAWINGS

The above features and advantages of the present invention will be moreapparent from the following description of certain preferred embodimentstaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view illustrating the sense amplifier region of aDRAM when the open bit line method is adopted in accordance with a firstpreferred embodiment of the present invention;

FIG. 2 is a schematic view illustrating the sense amplifier regionlayout of the circuit configuration of FIG. 1;

FIG. 3 is a schematic view illustrating the direction in which a changein the electric potential occurs due to a coupling noise generatedbetween local input/output (I/O) lines;

FIGS. 4A through 4D are diagrams illustrating potentials of four localinput/output (I/O) lines;

FIG. 5 is a schematic view illustrating a coupling noise generatedbetween local input/output (I/O) lines in a second embodiment of theinvention;

FIG. 6 is a schematic view illustrating a coupling noise generatedbetween local input/output (I/O) lines in a third embodiment of theinvention;

FIG. 7 is a schematic view illustrating a coupling noise generatedbetween local input/output (I/O) lines in a fourth embodiment of theinvention;

FIG. 8 is a diagram illustrating a sense amplifier region of the DRAMwhich adopts the folded bit line architecture in the related art;

FIG. 9 is a schematic view illustrating the layout of the circuitconfigurations of FIG. 8;

FIG. 10 is a schematic view illustrating the floating capacitancesgenerated between local input/output (I/O) lines when the localinput/output (I/O) lines are cut in a direction perpendicular to thelongitudinal direction along the line AA′ of FIG. 9;

FIG. 11 is a schematic view illustrating a coupling noise generatedbetween local input/output (I/O) lines;

FIGS. 12A through 12D are diagrams illustrating potentials of four localinput/output (I/O) lines;

FIG. 13 is a schematic view illustrating the sense amplifier region whenthe open bit line method is adopted;

FIG. 14 is a schematic view illustrating the circuit configurations ofFIG. 13;

FIG. 15 is a schematic view illustrating a coupling noise generatedbetween local input/output (I/O) lines when there is no power supplyline; and

FIG. 16 shows a change in the electric potential of each localinput/output (I/O) line when (0, 1, 0, 1) is adopted as the datacombination of (LIO0T, LIO1T, LIO2T, LIO3T).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before describing the present invention, the related art will beexplained in detail with reference to FIGS. 8, 9, 10, 13, and 14, inorder to facilitate the understanding of the present invention.

In known DRAMs, a folded bit line architecture has been adopted formemory cells and bit lines. FIG. 8 is a diagram illustrating a senseamplifier region of the DRAM which adopts the folded bit linearchitecture in the related art. Each true bit line BLL0T and each barbit line BLL0B shown in FIG. 8 are disposed in parallel, and the bitlines are disposed on the same side with respect to a sense amplifier.Here, the sense amplifier is shared between two left and right bit linepairs (bit line BLL0T, bit line BLL0B) and (bit line BLR0T, bit lineBLR0B) which interpose the sense amplifier between them. To amplify asmall signal from a memory cell connected to either one of the bit linepairs with the sense amplifier, the left and right bit line pairs areseparated from the sense amplifier by shared signals SHRL and SHRR,respectively.

In addition, a sense amplifier and a local input/output (I/O) line areconnected to each other by a Y switch signal. Two sets of bit line pairs(bit line BLL0T, bit line BLL0B) and (bit line BLL1T, bit line BLL1B) ortwo sets of bit line pairs (bit line BLR0T, bit line BLR0B) and (bitline BLR1T, bit line BLR1B) are connected to local input/output (I/O)line pairs (local input/output (I/O) line LIO0T, local input/output(I/O) line LIO0B) and (local input/output (I/O) line LIO1T, localinput/output (I/O) line LIO1B) by a Y switch MOS to which a Y switchsignal YS0 is input. Here, the local input/output (I/O) lines aredisposed in a direction perpendicular to the bit lines. In addition, thedifference potential between the local input/output (I/O) line pairs isamplified by two sub-amplifiers shown in FIG. 8, and the data obtainedas a result of the amplification is transmitted to the outside of thememory cell array by main IO lines MIO0 and MIO1.

FIG. 9 is a schematic view illustrating the layout of the circuitconfigurations of FIG. 8.

Each region in FIG. 9 is a region where the arrangement of an MOStransistor is conceptually illustrated, and corresponds to the schematicview illustrating the sense amplifier region in FIG. 8. That is,corresponding to FIG. 8, regions of a bit line equalizing MOSarrangement region 500, a sense amplifier PMOS arrangement region 501, asense amplifier control MOS arrangement region 502, a sense amplifierNMOS arrangement region 503, a Y switch MOS arrangement region 504, anda bit line equalizing MOS arrangement region 505 are disposed from theleft.

Here, four local input/output (I/O) lines are disposed in parallel inthe Y switch MOS arrangement region 504. Moreover, by this arrangementmethod, local input/output (I/O) lines adjacent to the localinput/output (I/O) line LIO1T are two of the local input/output (I/O)line LIO0T and the local input/output (I/O) line LIO0B, for example.However, since signals with the opposite phases are transmitted throughthe local input/output (I/O) line LIO0T and the local input/output (I/O)line LIO0B, coupling noises that have an effect on the localinput/output (I/O) line LIO1T disposed between the two localinput/output (I/O) lines are cancelled.

FIG. 10 is a schematic view illustrating the floating capacitancesgenerated between local input/output (I/O) lines when the localinput/output (I/O) lines are cut in a direction perpendicular to thelongitudinal direction along the line AA′ of FIG. 9. Here, the floatingcapacitances generated between the local input/output (I/O) lines aredenoted as floating capacitance C1, floating capacitance C2, andfloating capacitance C3. If the distance between local input/output(I/O) lines decreases as the mounting density of wiring lines increases,the floating capacitance between the local input/output (I/O) linesincreases. This causes a problem of coupling noise, and it is alsodisadvantageous in raising the speed of the DRAM.

In addition, the problem of coupling noise becomes more noticeable whenthe open bit line method is adopted for memory cells and bit lines.

In accordance with the open bit line method, each true bit line and eachbar bit line are disposed in opposite sides with respect to a senseamplifier interposed between them. FIG. 13 is a schematic viewillustrating the sense amplifier region when the open bit line method isadopted. In FIG. 13, in order to make the bit number of a DRAM memorycell equal to that in the folded bit line architecture shown in FIG. 8described previously, the following configurations are adopted. The bitline pairs are four pairs, for example, the first pair of bit line BL0Tand bit line BL0B, the second pair of bit line BL1T and bit line BL1B,the third pair of bit line BL2T and bit line BL2B, and the fourth pairof line bit BL3T and bit line BL3B. The local input/output (I/O) linepairs are four pairs, for example, the first pair of local input/output(I/O) line LIO0T and local input/output (I/O) line LIO0B, the secondpair of local input/output (I/O) line LIO0T and local input/output (I/O)line LIO0B, the first pair of local input/output (I/O) line LIO2T andlocal input/output (I/O) line LIO2B, and the fourth pair of localinput/output (I/O) line LIO0T and local input/output (I/O) line LIO3B.

FIG. 14 is a schematic view illustrating the circuit configurations ofFIG. 13. As shown in FIG. 14, a Y switch MOS arrangement region 102, abit line equalizing NMOS arrangement region 103, a sense amplifier NMOSarrangement region 104, a bit line equalizing PMOS arrangement region105, a sense amplifier PMOS arrangement region 106, a bit lineequalizing PMOS arrangement region 107, a sense amplifier control MOSarrangement region 108, a sense amplifier NMOS arrangement region 109, abit line equalizing NMOS arrangement region 110, and a Y switch MOSarrangement region 111 are disposed from the left. In accordance withthe open bit line method, the Y switch MOS arrangement regions 102 and111 need to be separated as true and bar and be disposed at thepositions closest to bit lines. Accordingly, for the local input/output(I/O) lines, four true and four bars are disposed in parallel in the Yswitch MOS arrangement region.

The open bit line method is similar to the known folded bit linearchitecture in that four local input/output (I/O) lines are disposed inparallel. However, for the two inside local input/output (I/O) lines, ifsignals on local input/output (I/O) lines located at both sides thereofare not signals with opposite phases, the amount of coupling noiseincreases compared with that in the related art. For example, whensignals with an opposite phase are transmitted through both the localinput/output (I/O) line LIO0T and the local input/output (I/O) lineLIO2T which are adjacent to the local input/output (I/O) line LIO1T, thelocal input/output (I/O) line LIO1T receives a coupling noise from thelocal input/output (I/O) lines located at both the sides. As a result,the amount of signal is reduced.

If wiring lines having an electric potential fixed to the power supplypotential or ground potential or signal lines having a predeterminedfixed electric potential during the period for which a coupling noise isreceived are disposed on both sides of all wiring lines, which aredisposed at extremely narrow distances like local input/output (I/O)lines of the DRAM, so as to be adjacent to wiring lines that receivenoises as described above, the wiring region is increased andaccordingly, the area of the entire DRAM chip is increased. This isagainst the high integration.

The invention will be now described herein with reference toillustrative embodiments. Those skilled in the art will recognize thatmany alternative embodiments can be accomplished using the teaching ofthe present invention and that the invention is not limited to theembodiments illustrated for explanatory purpose.

In one embodiment, a semiconductor device may include, but is notlimited to, a first signal line, a second signal line, and a firstshield line. The first signal line is supplied with a first signal. Thefirst signal is smaller in amplitude than a potential difference betweena power potential and a reference potential. The second signal line isdisposed in a first side of the first signal line. The second signalline is supplied with a second signal. The second signal is smaller inamplitude than the potential difference. The first shield line isdisposed in a second side of the first signal line. The second side isopposite to the first side. The first shield line reduces a couplingnoise that is applied to the first shield line from the second side. Thefirst shield line prevents the first signal line from receiving acoupling noise from the second side of the first signal line, whereinthe second side is opposite to the first side in which the second signalline is disposed. This arrangement does not need a pair of shield linesare disposed both sides of each of the signal lines. Namely, thisarrangement does not need a large number of shield lines.

In another embodiment, a semiconductor device may include, but is notlimited to, a plurality of signal lines and at least one line. Theplurality of signal lines extends substantially in parallel to eachother. The plurality of signal lines is given signals that are smallerin amplitude than a potential difference between a power potential and aground potential. The at least one line is maintained at a fixedpotential. The at least one line is disposed in an opposite side of oneof the signal lines to a side in which another of the signal lines isdisposed. The shield line prevents the signal line from receiving acoupling noise from the second side of the signal line, wherein thesecond side is opposite to the first side in which the second signalline is disposed. This arrangement does not need a pair of shield linesare disposed both sides of each of the signal lines. Namely, thisarrangement does not need a large number of shield lines.

In still another embodiment, a semiconductor device may include, but isnot limited to, a plurality of signal lines and at least one shieldline. The plurality of signal lines extends substantially in parallel toeach other. The plurality of signal lines is given signals that aresmaller in amplitude than a potential difference between a powerpotential and a reference potential. The at least one shield line ismaintained at a fixed potential. Each of the plurality of signal linesis disposed between adjacent another of the plurality of signal linesand any one of the at least one shield line and a signal-line-free area.The signal-line-free area is free of the others of the plurality ofsignal lines and also free of any signal line which is given a signalthat is smaller in amplitude than the potential difference. The shieldline prevents the signal line from receiving a coupling noise from thesecond side of the signal line, wherein the second side is opposite tothe first side in which the second signal line is disposed. Thisarrangement does not need a pair of shield lines are disposed both sidesof each of the signal lines. Namely, this arrangement does not need alarge number of shield lines.

First Embodiment

FIG. 1 is a schematic view illustrating the sense amplifier region of aDRAM when the open bit line method is adopted. In accordance with theopen bit line method, each true bit line and each bar bit line aredisposed in opposite sides with respect to a sense amplifier interposedbetween them. In FIG. 1, true bit lines BL0T, BL1T, BL2T, and BL3T aredisposed on the left sides of sense amplifiers, and bar bit lines BL0B,BL1B, BL2B, and BL3B are disposed on the right sides of the senseamplifiers, respectively. The true bit lines and the bar bit lines formpairs and are connected to sense amplifier 10, 11, 12, and 13,respectively.

Each sense amplifier serves to amplify the difference potentialgenerated between the bit lines of the bit line pair after signals areoutput from memory cells to the bit lines after selection of a wordline. In addition, since the bit lines of each bit line pair need tohave the same electric potential before the selection of the word line,the bit lines of each bit line pair are maintained to have the sameelectric potential by bit line equalizers 20, 21, 22, and 23. At thepoint of time when the difference potential is generated between the bitlines of each bit line pair by a sense amplifier control MOS circuit(not shown) after activation of the sense amplifier, the bit line pairsare electrically connected to local input/output (I/O) line pairs by Yswitch MOSs 30, 31, 32, 33, 34, 35, 36, and 37 controlled by a Y switchsignal YS0. In FIG. 1, the four bit line pairs are connected to fourlocal input/output (I/O) line pairs. The first pair of bit line BL0T andbit line BL0B are connected to the first pair of local input/output(I/O) line LIO0T and local input/output (I/O) line LIO0B. The secondpair of bit line BL1T and bit line BL1B are connected to the second pairof local input/output (I/O) line LIO1T and local input/output (I/O) lineLIO1B. The third pair of bit line BL2T and bit line BL2B are connectedto the third pair of local input/output (I/O) line LIO2T and localinput/output (I/O) line LIO2B. The fourth pair of bit line BL3T and bitline BL3 are connected to the fourth pair of local input/output (I/O)line LIO3T and local input/output (I/O) line LIO3B. In addition, bitline pairs not shown are connected to the corresponding localinput/output (I/O) line pairs through respective Y switch MOSs notshown. These bit line pairs are amplified by corresponding senseamplifiers not shown, but the bit line pairs are not electricallyconnected to the respective local input/output (I/O) line pairs becauseY switch signals YS1, YSn-1, and YSn are not selected.

The local input/output (I/O) line pairs are disposed in a directionperpendicular to the bit lines. The difference potentials between thelocal input/output (I/O) lines of the local input/output (I/O) linepairs are amplified by four sub-amplifiers 40, 41, 42, and 43 shown inFIG. 1. The data is transmitted to the outside of the memory cell arrayas main IO lines MIO0, MIO1, MIO2, and MIO3.

This embodiment is different from the related art. A power supply line100 is disposed between the local input/output (I/O) lines LIO1T andLIO2T, which are two inside local input/output (I/O) lines of the fourlocal input/output (I/O) lines, in parallel with the local input/output(I/O) lines. A power supply line 101 is disposed between the localinput/output (I/O) lines LIO1B and LIO2B, which are two inside localinput/output (I/O) lines of the four local input/output (I/O) lines, inparallel with the local input/output (I/O) lines.

FIG. 2 is a schematic view illustrating the sense amplifier regionlayout of the circuit configuration of FIG. 1. Each region shown in FIG.2 is a region of a MOS transistor existing between a true bit line and abar bit line. Here, a Y switch MOS arrangement region 102, a Y switchMOS arrangement region 111, a bit line equalizing NMOS arrangementregion 103, a bit line equalizing NMOS arrangement region 110, a senseamplifier NMOS arrangement region 104, and a sense amplifier NMOSarrangement region 109 are disposed at true or bar side so that the bitline capacitances of true bit line and bar bit line are not unbalanced.The true side has the Y switch MOS arrangement region 102, the bit lineequalizing NMOS arrangement region 103, the sense amplifier NMOSarrangement region 104. The bar side has the Y switch MOS arrangementregion 111, the bit line equalizing NMOS arrangement region 110, and thesense amplifier NMOS arrangement region 109. In addition, in order toreduce the separation region between an NMOS and a PMOS so that thewidth of the sense amplifier region has no increase. A bit lineequalizing PMOS arrangement region 105, a bit line equalizing PMOSarrangement region 107, and a sense amplifier PMOS arrangement region106 are gathered in the middle of the region. Moreover, for a senseamplifier control MOS arrangement region 108, the PMOS region isdisposed on the true side and the NMOS region is disposed on the barside when both the PMOS and the NMOS are used.

Moreover, for the local input/output (I/O) lines, local input/output(I/O) lines LIO0T, LIO1T, LIO2T, and LIO3T are disposed in the Y switchMOS arrangement region close to the true bit line, and localinput/output (I/O) lines LIO0B, LIO1B, LIO2B, and LIO3B are disposed inthe Y switch MOS arrangement region close to the bar bit line.

In the present embodiment, the power supply line 100 is disposed betweenthe true side local input/output (I/O) lines LIO1T and LIO2T in parallelwith the local input/output (I/O) lines, and the power supply line 101is disposed between the bar side local input/output (I/O) lines LIO1Band LIO2B in parallel with the local input/output (I/O) lines.

FIG. 3 is a schematic view illustrating the direction in which a changein the electric potential occurs due to a coupling noise generatedbetween local input/output (I/O) lines. A local input/output (I/O) lineas a source of noise generation and a local input/output (I/O) linewhich receives a noise are shown by arrows. For example, the localinput/output (I/O) line LIO0T receives a noise from the localinput/output (I/O) line LIO1T, and the local input/output (I/O) lineLIO1T receives a noise from the LIO0T on the contrary. On the otherhand, the local input/output (I/O) line LIO1T does not receive acoupling noise from the local input/output (I/O) line LIO2T because achange in the electric potential of the local input/output (I/O) lineLIO2T is shielded by the power supply line 100. Similarly, the localinput/output (I/O) line LIO2T does not receive a coupling noise from thelocal input/output (I/O) line LIO1T due to the power supply line 100.Also on the bar side, the local input/output (I/O) lines LIO1B and LIO2Bdo not receive coupling noises from each other due to the power supplyline 101.

This situation is shown in FIGS. 4A to 4D in more detail. In thisexample, there are four local input/output (I/O) line pairs.Accordingly, there are in total 16 combinations as the combination ofLIO0T, LIO1T, LIO2T, and LIO3T of data of the local input/output (I/O)lines. The data of the local input/output (I/O) lines LIO2T and LIO3Tare set to be 0 and 1, respectively, for the sake of convenience oflater comparison with a known example.

Explanations on the bar side local input/output (I/O) lines LIO0B,LIO1B, LIO2B, and LIO3B will be omitted since signals on the bar sidelocal input/output (I/O) lines have opposite phases to those of the trueside local input/output (I/O) lines.

In FIGS. 4A to 4D, the electric potential VI indicates an electricpotential of each local input/output (I/O) line before the localinput/output (I/O) line is connected to the sense amplifier. Moreover,VL and VH indicate low and high levels of an electric potential of eachlocal input/output (I/O) line to reach when the sub-amplifier isactivated, respectively, after the local input/output (I/O) line isconnected to the sense amplifier. In addition, the arrows in FIGS. 4A to4D indicate a change in the electric potential of each localinput/output (I/O) line. The arrow shown by a one-dotted chain lineindicates an electric potential change (change from VI to VL or VH) whena coupling noise is not received, and the arrow shown by a solid lineindicates an actual change in the electric potential.

When the combination of data of local input/output (I/O) lines is (0, 0,0, 1) as shown in FIG. 4A, the electric potential of the localinput/output (I/O) line LIO0T located at the outermost side of the fourlocal input/output (I/O) lines is changed to an electric potential lowerthan VL due to the floating capacitance C1 between the localinput/output (I/O) line LIO0T and the local input/output (I/O) lineLIO1T located next to the local input/output (I/O) line LIO0T inwardly.The difference between the electric potential and VL is a coupling noiseVN. Similarly, the electric potential of the local input/output (I/O)line LIO1T is changed to an electric potential lower than VL by VN dueto the floating capacitance C1 between the local input/output (I/O)lines LIO0T and LIO1T.

In this case, the local input/output (I/O) line LIO1T does not receive acoupling noise from the local input/output (I/O) line LIO2T due to thepower supply line 100 and receives only a coupling noise from the localinput/output (I/O) line LIO0T.

On the other hand, for the local input/output (I/O) lines LIO2T andLIO3T, the directions of electric potential changes are opposite tothose described above. Accordingly, the electric potential of the localinput/output (I/O) line LIO2T is changed to an electric potential higherthan VL by VN, and the electric potential of the local input/output(I/O) line LIO3T is changed to an electric potential lower than VH byVN. Similarly, the local input/output (I/O) line LIO2T does not receivea coupling noise from the local input/output (I/O) line LIO1T due to thepower supply line 100.

When the combination of data of local input/output (I/O) lines is (0, 1,0, 1) as shown in FIG. 4B, the electric potentials of the localinput/output (I/O) lines LIO0T and LIO1T are changed similar to those ofthe local input/output (I/O) lines LIO2T and LIO3T when the combinationis (0, 0, 0, 1). That is, the electric potential of the localinput/output (I/O) line LIO0T is changed to an electric potential higherthan VL by VN, and the electric potential of the local input/output(I/O) line LIO1T is changed to an electric potential lower than VH byVN.

When the combination of data of local input/output (I/O) lines is (1, 0,0, 1) as FIG. 4C, the electric potentials of the local input/output(I/O) lines LIO0T and LIO3T are changed to electric potentials lowerthan VH by VN, and the electric potentials of the local input/output(I/O) lines LIO1T and LIO2T are changed to electric potentials higherthan VL by VN. In addition, when the combination of data of localinput/output (I/O) lines is (1, 1, 0, 1), the local input/output (I/O)lines LIO0T and LIO1T are in the complementary relationship.Accordingly, the electric potentials of the local input/output (I/O)lines LIO0T and LIO1T are changed to values higher than VH by VN as FIG.4D.

Next, comparison with a coupling noise in the open bit line method asshown FIG. 14 when the power supply lines 100 and 101 do not exist willbe performed.

FIG. 15 is a schematic view illustrating a coupling noise generatedbetween local input/output (I/O) lines when there is no power supplyline. FIG. 15 is similar to FIG. 3 in that a local input/output (I/O)line as a source of noise generation and a local input/output (I/O) linewhich receives a noise are shown by arrows. In FIG. 15, however, therelationship in which each of adjacent local input/output (I/O) lines isa noise source and also receives a noise is additionally shown by adouble-pointed arrow. For example, the local input/output (I/O) lineLIO1T gives a coupling noise to the local input/output (I/O) line LIO2Tand also receives a coupling noise from the LIO2T.

FIG. 16 shows a change in the electric potential of each localinput/output (I/O) line when (0, 1, 0, 1) is adopted as the datacombination of (LIO0T, LIO1T, LIO2T, LIO3T).

In addition, an explanation on the bar side local input/output (I/O)lines LIO0B, LIO1B, LIO2B, and LIO3B will be omitted since signals onthe bar side local input/output (I/O) lines have opposite phases tothose of the true side local input/output (I/O) lines. Similar to theabove-described case, the electric potential of each local input/output(I/O) line is assumed to be VI immediately before the local input/output(I/O) line is connected to a sense amplifier, and the electricpotentials VL and VH indicate low and high levels of an electricpotential to reach when the sub-amplifier is activated, respectively,after the local input/output (I/O) line is connected to the senseamplifier. In this combination, the local input/output (I/O) line LIO0Tlocated at the outer side among the four local input/output (I/O) linesreceives a coupling noise VN1 due to the local input/output (I/O) lineLIO1T located next to the local input/output (I/O) line LIO0T inwardly,and the local input/output (I/O) line LIO3T located at the outer sideamong the four local input/output (I/O) lines receives a coupling noiseVN1 due to the local input/output (I/O) line LIO2T located next to thelocal input/output (I/O) line LIO3T inwardly.

On the other hand, the local input/output (I/O) line LIO1T located nextto the local input/output (I/O) line LIO0T inwardly receives a couplingnoise VN2 because the electric potentials of the adjacent localinput/output (I/O) lines LIO0T and LIO2T are changed to VL even thoughthe electric potential of the local input/output (I/O) line LIO1T ischanged to VH. When the values of VN1 and VN2 are compared with theprevious amount of change VN, the coupling noise VN1 is almost equal toVN and the coupling noise VN2 is twice the coupling noise VN assumingthat the distances between local input/output (I/O) lines and the wiringlengths of the local input/output (I/O) lines are equal.

Accordingly, by disposing the power supply line 100 between the localinput/output (I/O) lines LIO1T and LIO2T, the local input/output (I/O)line LIO1T does not receive a coupling noise from the local input/output(I/O) lines, which are located at both sides of the local input/output(I/O) line LIO1T, any more. As a result, the amount of coupling noisecan be greatly reduced.

Next, the case where it is compared with the folded bit linearchitecture (FIG. 9) will be described.

FIG. 11 is a schematic view illustrating a coupling noise generatedbetween local input/output (I/O) lines.

The point that a local input/output (I/O) line as a source of noisegeneration and a local input/output (I/O) line which receives a noiseare shown by arrows is the same as that described above. In addition, achange in the electric potential of each local input/output (I/O) lineis shown in FIGS. 12A to 12D. In FIGS. 12A to 12D, VI indicates theelectric potential of each local input/output (I/O) line is VIimmediately before the local input/output (I/O) line is connected to asense amplifier, and VL and VH indicate low and high levels of anelectric potential to reach when the sub-amplifier is activated,respectively, after the local input/output (I/O) line is connected tothe sense amplifier. In this example, there are two pairs of localinput/output (I/O) lines. Accordingly, there are four combinations thatcan be set when (LIO0, LIO1) are considered as the combination of data.

When the combination of data of local input/output (I/O) lines is (0, 0)as shown in FIG. 12A, the electric potential of the local input/output(I/O) line LIO0T located at the outermost side of the four localinput/output (I/O) lines is changed to an electric potential lower thanVL due to the floating capacitance C1 between the local input/output(I/O) line LIO0T and the local input/output (I/O) line located next tothe local input/output (I/O) line LIO0T inwardly. The difference betweenthe electric potential and VL is a coupling noise VN3. Similarly, theelectric potential of the outside local input/output (I/O) line LIO1B ischanged to an electric potential higher than VH by VN3 due to the localinput/output (I/O) line LIO0B, which is located next to the localinput/output (I/O) line LIO1B inwardly, and the floating capacitance C3.

On the other hand, when the combination of data of local input/output(I/O) lines is (1, 0) as shown in FIG. 12B, each of the localinput/output (I/O) lines LIO0T and LIO1B located at the outer sidesreceives a coupling noise from the local input/output (I/O) line locatednext to each of the local input/output (I/O) lines LIO0T and LIO1Binwardly in a direction in which the amount of signal is decreased.

Similarly, when the combination of data of local input/output (I/O)lines is (0, 1), a coupling noise is received in a direction in whichthe amount of signal is decreased as shown in FIG. 12C. In addition,when the combination of data of local input/output (I/O) lines is (1,1), a coupling noise is received in a direction in which the amount ofsignal is increased as shown in FIG. 12D.

Therefore, in the folded bit line architecture, when the combination ofdata of local input/output (I/O) lines is different in the localinput/output (I/O) lines LIO0T and LIO1T, a coupling noise is receivedin a direction in which the amount of signal is decreased.

Assuming that the local input/output (I/O) lines and the wiring lengthsare equal for comparison with the embodiment, VN3 is almost equal to VN.

Thus, according to the semiconductor device of the present embodiment, aplurality of signal lines includes a first set of local input/output(I/O) lines LIO0T, LIO1T, LIO2T, and LIO3T and a second set of localinput/output (I/O) lines LIO0B, LIO1B, LIO2B, and LIO3B. The localinput/output (I/O) lines are disposed in parallel to each other. Signalsare transmitted through each of the local input/output (I/O) lines. Thesignals may have amplitude that is smaller than the signal amplitudescorresponding to the power supply potential and the ground potential.Wiring lines, for example, power supply lines 100 and 101 are providedwhich maintain a predetermined electric potential. The wiring lines, forexample, the power supply lines 100 and 101 are provided at only oneside where the signal lines such as the local input/output (I/O) linesLIO1T and LIO1B are opposite to the other signal lines such as localinput/output (I/O) lines LIO2T and LIO2B.

As a result, the signal line such as the local input/output (I/O) lineLIO1T receives only a coupling noise from the adjacent signal line suchas the local input/output (I/O) line LIO0T. In addition, the signallines such as the local input/output (I/O) lines LIO2T, LIO1B, and LIO2Breceive only coupling noises from one side or from the signal lines suchas the local input/output (I/O) lines LIO3T, LIO0B, and LIO3B which areadjacent to the signal lines (local input/output (I/O) lines LIO2T,LIO1B, and LIO2B), respectively. Namely, the local input/output (I/O)line LIO2T receives only a coupling noise from the local input/output(I/O) line LIO3T which is adjacent to the local input/output (I/O) lineLIO2T. The local input/output (I/O) line LIO1B receives only a couplingnoise from the local input/output (I/O) line LIO0B which is adjacent tothe local input/output (I/O) line LIO1B. The local input/output (I/O)line LIO2B receives only a coupling noise from the local input/output(I/O) line LIO3B which is adjacent to the local input/output (I/O) lineLIO2B. Thus, the signal line such as the local input/output (I/O) linedoes not receive a coupling noise from signal lines such as the localinput/output (I/O) lines on both sides of the signal line, which areadjacent to the signal line. Accordingly, the amount of coupling noisecan be suppressed to almost the same as that when the above-describedfolded dead bit line method is adopted. As a result, a DRAM capable ofrealizing the high speed can be obtained. In addition, since it is notnecessary to provide a power supply line between all local input/output(I/O) lines, it is possible to prevent an increase in the chip areacaused by an increase in the area of a wiring region.

Furthermore, in the above-described embodiment, the power supply line isdisposed between the local input/output (I/O) lines LIO1T and LIO2T,which are two inside local input/output (I/O) lines of the four parallellocal input/output (I/O) lines, and between the local input/output (I/O)lines LIO1B and LIO2B, which are two inside local input/output (I/O)lines of the four parallel local input/output (I/O) lines. However, thesame effect can be obtained even if the power supply is disposed betweenthe local input/output (I/O) lines LIO0T and LIO1T, between the localinput/output (I/O) lines LIO2T and LIO3T, between the local input/output(I/O) lines LIO0B and LIO1B, and between the local input/output (I/O)lines LIO2B and LIO3B.

In this case, the signal line such as the local input/output (I/O) lineLIO1T receives only a coupling noise from the adjacent signal line suchas the local input/output (I/O) line LIO2T. In addition, the signallines such as the local input/output (I/O) lines LIO2T, LIO1B, and LIO2Breceive only coupling noises from one side or from the signal lines suchas the local input/output (I/O) lines LIO1T, LIO2B, and LIO1B which areadjacent to the signal lines such as the local input/output (I/O) linesLIO2T, LIO1B, and LIO2B, respectively. Namely, the local input/output(I/O) line LIO2T receives only a coupling noise from the localinput/output (I/O) line LIO1T which is adjacent to the localinput/output (I/O) line LIO2T. The local input/output (I/O) line LIO1Breceives only a coupling noise from the local input/output (I/O) lineLIO2B which is adjacent to the local input/output (I/O) line LIO1B. Thelocal input/output (I/O) line LIO2B receives only a coupling noise fromthe local input/output (I/O) line LIO1B which is adjacent to the localinput/output (I/O) line LIO2B. Accordingly, similarly, a signal linesuch as the local input/output (I/O) line does not receive a couplingnoise from signal lines such as the local input/output (I/O) lines onboth sides of the signal line, which are adjacent to the signal line.

Second Embodiment

FIG. 5 is a schematic view illustrating a coupling noise generatedbetween local input/output (I/O) lines in a second embodiment of theinvention. The different of the second embodiment from the firstembodiment is that the power supply lines 100 and 101 in the firstembodiment are replaced with signal lines 200 and 201. Any signal linemay be used as the signal lines 200 and 201 as long as it is not asignal line activated during a period for which a small signal istransmitted to a local input/output (I/O) line. It may be a fixedelectric potential of a ground potential, a power supply potential, oran intermediate electric potential between two electric potentials. Inthe present embodiment, the disposed signal lines 200 and 201 show theeffect as shield wiring lines like the power supply lines 100 and 101.In addition, the signal lines 200 and 201 may be used in the senseamplifier region or may be used for a signal simply passing through thesense amplifier region. Accordingly, signal wiring lines can beeffectively used.

Third Embodiment

FIG. 6 is a schematic view illustrating a coupling noise generatedbetween local input/output (I/O) lines in a third embodiment of theinvention. While one kind of power supply line has been used in thefirst embodiment, two different power supply lines are disposed in thepresent embodiment. First and second power supply lines 300 and 302 aredisposed between local input/output (I/O) lines LIO1T and LIO2T, andfirst and second power supply lines 301 and 303 are disposed betweenlocal input/output (I/O) lines LIO1B and LIO2B. According to the presentembodiment, since the electric potentials of the first and second powersupply lines are fixed electric potentials, the effect as shield wiringlines is obtained. In addition, the present embodiment is particularlyeffective in the case where power supply lines with the differentelectric potentials are needed in a sense amplifier region.

Fourth Embodiment

FIG. 7 is a schematic view illustrating a coupling noise generatedbetween local input/output (I/O) lines in a fourth embodiment of theinvention. FIG. 7 shows the case as follows. There are provided sixlocal input/output (I/O) line pairs. The first pair of the localinput/output (I/O) line pairs are local input/output (I/O) line LIO0Tand local input/output (I/O) line LIO0B. The second pair of the localinput/output (I/O) line pairs are local input/output (I/O) line LIO1Tand local input/output (I/O) line LIO1B. The third pair of the localinput/output (I/O) line pairs are local input/output (I/O) line LIO2Tand local input/output (I/O) line LIO2B. The fourth pair of the localinput/output (I/O) line pairs are local input/output (I/O) line LIO3Tand local input/output (I/O) line LIO3B. The fifth pair of the localinput/output (I/O) line pairs are local input/output (I/O) line LIO4Tand local input/output (I/O) line LIO4B. The sixth pair of the localinput/output (I/O) line pairs are local input/output (I/O) line LIO0Tand local input/output (I/O) line LIO0B.

It does not need to be limited to the above number, and it is a numberto be appropriately determined according to the number of localinput/output (I/O) lines of a DRAM or the like. That is, when the numberof local input/output (I/O) line pairs is five or more, a power supplyline is disposed for every two local input/output (I/O) lines and thepower supply line is disposed on only the one side for all of the localinput/output (I/O) lines in the embodiment. FIG. 7 shows the case wherethe number of local input/output (I/O) line pairs is six. In this case,for six local input/output (I/O) lines existing on the true side, apower supply line 400 is disposed between the second and third localinput/output (I/O) lines LIO1T and LIO2T and a power supply line 401 isdisposed between the fourth and fifth local input/output (I/O) linesLIO3T and LIO4T. On the other hand, for six local input/output (I/O)lines existing on the bar side, a power supply line 402 is disposedbetween the second and third local input/output (I/O) lines LIO1B andLIO2B and a power supply line 403 is disposed between the fourth andfifth local input/output (I/O) lines LIO3B and LIO4B. Accordingly, thelocal input/output (I/O) lines which interpose a power supply linetherebetween do not receive coupling noises from each other. Accordingto the present embodiment, even if the number of local input/output(I/O) line increases, it is not necessary to dispose the shield wiringlines adjacent to all local input/output (I/O) lines. Therefore, asignificant increase in the wiring region does not occur. As a result,it is possible to prevent an increase in the chip area caused by anincrease in the number of local input/output (I/O) lines. In addition,although the example where the power supply line is disposed has beendescribed in the present embodiment, a signal line with a fixed electricpotential during a period for which a local input/output (I/O) linereceives a coupling noise may be disposed like the other embodimentsdescribed above, or it is also possible to dispose two or more kinds ofpower supply lines. In addition, these may be appropriately combined.

It is apparent that the present invention is not limited to the aboveembodiments, but may be modified and changed without departing from thescope and spirit of the invention.

1. A semiconductor device comprising: a first signal line being suppliedwith a first signal, the first signal being smaller in amplitude than apotential difference between a power potential and a referencepotential; a second signal line being disposed in a first side of thefirst signal line, the second signal line being supplied with a secondsignal, the second signal being smaller in amplitude than the potentialdifference; and a first shield line being disposed in a second side ofthe first signal line, the second side being opposite to the first side,the first shield line reducing a coupling noise that is applied to thefirst shield line from the second side.
 2. The semiconductor deviceaccording to claim 1, wherein the second signal line is substantiallyparallel to the first signal line, the second signal line is adjacent tothe first signal line, the first shield line is substantially parallelto the first and second signal lines, and the first shield line isadjacent to the first signal line.
 3. The semiconductor device accordingto claim 1, wherein the first shield line is maintained at a fixedpotential at least a period of time when the first signal line receivesa coupling noise from the second signal line.
 4. The semiconductordevice according to claim 3, wherein the first shield line comprises atleast one of a power line, a ground line, and a signal line that ismaintained at a fixed potential.
 5. The semiconductor device accordingto claim 1, wherein the first shield line is substantially parallel tothe first and second signal lines.
 6. The semiconductor device accordingto claim 1, further comprising: a first sense amplifier eclecticallycoupled to the first signal line, the first sense amplifier beingeclectically separated from the first shield line; and a second senseamplifier eclectically coupled to the second signal line, the secondsense amplifier being eclectically separated from the first shield line.7. The semiconductor device according to claim 6, further comprising: afirst equalizer eclectically coupled to the first signal line, the firstequalizer being eclectically separated from the first shield line; and asecond equalizer eclectically coupled to the second signal line, thesecond equalizer being eclectically separated from the first shieldline.
 8. The semiconductor device according to claim 6, furthercomprising: memory cells; first and second bit lines connected to thememory cells, the first and second bit lines being connected to thefirst and second sense amplifiers respectively, wherein the first andsecond sense amplifiers amplify signals of the first and second bitlines respectively; first and second switches connected through thefirst and second bit lines to the first and second amplifiersrespectively, wherein the first and second signal lines are first andsecond input/output lines that are connected via the first and secondswitches and the first and second bit lines to the first and secondamplifiers respectively.
 9. The semiconductor device according to claim1, further comprising: a first sub amplifier eclectically coupled to thefirst signal line, the first sub amplifier being eclectically separatedfrom the first shield line; and a second sub amplifier eclecticallycoupled to the second signal line, the second sub amplifier beingeclectically separated from the first shield line.
 10. The semiconductordevice according to claim 1, wherein the second signal line is disposedbetween the first signal line and a signal-line-free area, thesignal-line-free area is free of any signal line which is given a signalthat is smaller in amplitude than the potential difference.
 11. Thesemiconductor device according to claim 1, further comprising: a secondshield line substantially parallel to the first and second signal linesand the first shield line, the second shield line being adjacent to thesecond signal line, wherein the second signal line is disposed betweenthe first signal line and the second shield line.
 12. The semiconductordevice according to claim 11, further comprising: a third signal linebeing substantially parallel to the first and second signal lines andthe first and second shield lines, the third signal line being adjacentto the second shield line, the third signal line being supplied with athird signal having a third amplitude that is smaller than the potentialdifference; and a fourth signal line being substantially parallel to thefirst, second and third signal lines and the first and second shieldlines, the fourth signal line being adjacent to the third signal line,the fourth signal line being supplied with a fourth signal having afourth amplitude that is smaller than the potential difference, whereinthe third signal line is disposed between the second shield line and thefourth signal line.
 13. The semiconductor device according to claim 12,wherein the fourth signal line is disposed between the fourth signalline and a signal-line-free area.
 14. The semiconductor device accordingto claim 11, further comprising: a third shield line substantiallyparallel to the first, second, third and fourth signal lines and thefirst and second shield lines, the third shield line being adjacent tothe fourth signal line, wherein the fourth signal line is disposedbetween the third signal line and the third shield line.
 15. Thesemiconductor device according to claim 1, wherein the referencepotential is a ground potential.
 16. A semiconductor device comprising:a plurality of signal lines that extend substantially in parallel toeach other, the plurality of signal lines being given signals that aresmaller in amplitude than a potential difference between a powerpotential and a ground potential; and at least one line being maintainedat a fixed potential, the at least one line being disposed in anopposite side of one of the signal lines to a side in which another ofthe signal lines is disposed.
 17. The semiconductor device according toclaim 16, wherein the at least one line comprises at least one of apower line, a ground line, and a signal line that is maintained at afixed potential.
 18. The semiconductor device according to claim 16,wherein the plurality of signal lines comprise input/output lines whichare connected via switching signals to bit lines, the bit linesconnecting memory cells and sense amplifiers which amplify the signalson the bit lines.
 19. A semiconductor device comprising: a plurality ofsignal lines that extend substantially in parallel to each other, theplurality of signal lines being given signals that are smaller inamplitude than a potential difference between a power potential and areference potential; and at least one shield line being maintained at afixed potential, wherein each of the plurality of signal lines isdisposed between adjacent another of the plurality of signal lines andany one of the at least one shield line and a signal-line-free area, thesignal-line-free area being free of the others of the plurality ofsignal lines and also free of any signal line which is given a signalthat is smaller in amplitude than the potential difference.
 20. Thesemiconductor device according to claim 19, further comprising: aplurality of memory cells; a plurality of bit lines connected to theplurality of memory cells; a plurality of sense amplifiers eclecticallycoupled to the plurality of bit lines, the plurality of sense amplifiersamplifying signals of the plurality of bit lines, the plurality of senseamplifiers being eclectically separated from the at least one shieldline; a plurality of switches connected through the plurality of bitlines to the plurality of sense amplifiers, wherein the plurality ofsignal lines are input/output lines that are connected via the pluralityof switches and the plurality of bit lines to the plurality of senseamplifiers.